People who are genetically predisposed to developing schizophrenia are also more likely to use marijuana.

Nature World News, Jun 24, 2014

The study, conducted by scientists at the King's College London, explains the link between marijuana-use and schizophrenia.

Schizophrenia is characterized by visual and auditory hallucinations. According to estimates, 1 in every 100 people suffers from this condition. Research has shown that people with schizophrenia are more likely to use marijuana and that the drug users have a higher risk of developing the disorder. A causal link between the two hasn't been established as yet.

"Studies have consistently shown a link between cannabis use and schizophrenia. We wanted to explore whether this is because of a direct cause and effect, or whether there may be shared genes which predispose individuals to both cannabis use and schizophrenia," said Robert Power, lead author from the MRC Social, Genetic and Developmental Psychiatry (SGDP) Centre at the Institute of Psychiatry at King's.

The study was based on data from 2,082 healthy people, of whom 1,011 had used cannabis. Researchers looked at each participant's genetic risk profile or the number of genes linked to schizophrenia that the person carried.

Researchers found that people who were genetically predisposed to schizophrenia were more likely to use the drug and also use it in larger amounts than other people.

"We know that cannabis increases the risk of schizophrenia. Our study certainly does not rule this out, but it suggests that there is likely to be an association in the other direction as well - that a predisposition to schizophrenia also increases your likelihood of cannabis use," Power said in a news release.

The National Institutes of Health, Australian National health and Medical Research Council and others funded the research. It was published in the journal Molecular Psychiatry.